A modern internal combustion engine include many moving parts, such as reciprocating and rotating parts, which may cause unbalanced forces to be exerted on the engine. It is generally desirable to cancel or balance these forces where possible to extend the life of the engine components and to improve the comfort of users of the vehicle.
Balancing of the engine forces is often achieved with one or more balancer shafts which comprise eccentrically weighted components. The eccentrically weighted components are designed to apply equal and opposite forces to those exerted on the engine by other components when the balancer shaft is rotated. Thus, the net reciprocating forces applied to the engine during operation may be substantially reduced.
Axial forces may arise in balancer shafts due to eccentric weighting. The forces cause the balancer shaft to shift in an axial direction. Axial forces can also be applied to the balancer shaft by the driving mechanism of the shaft, such as helical gears. In order to reduce or prevent this movement, balancer shafts utilize thrust control.
Conventional methods of controlling the axial movement of balancer shafts include the use of thrust washers and radial grooves. Thrust washers are positioned between two components of a balancer shaft assembly such that potential axial movement distance is reduced. Thrust washers add weight, dimension, cost, and manufacturing steps to balancer shaft assemblies. Radial grooves can also be used in which part of the balancer shaft journal fits within the radial groove such that axial movement is limited. This approach requires larger journal surfaces, additional weight, and manufacturing of the balancer shaft. In view of the numerous constraints applied to the design of modern internal combustion engines, it will be understood that improvements in the field of thrust control of balancer shafts are desirable.
However, the inventors herein have recognized potential issues with conventional systems. As an example, there are numerous conflicting packaging constraints in the lower end of the engine which do not permit the use of conventional thrust control features. Thus, the combining of the thrust control into the bearing cap provides a space-saving, weight, and simplicity advantage.
In one example, the issues described above may be addressed by a system for a balancer shaft assembly for an internal combustion engine comprising: a bearing cap and a balancer shaft configured to rotate within a bearing comprising the bearing cap. The bearing cap comprises first and second thrust control faces on opposing sides of the bearing cap. The first and second thrust control faces form the extreme axial faces of the bearing cap. The balancer shaft comprises first and second components, at least one of the first and second components being operable to balance the internal combustion engine. The first and second components are arranged on the opposing sides of the bearing cap to thereby constrain axial movement of the balancer shaft. In this way, the thrust control faces control axial movement of the balancer shaft in a simple, compact, and low weight manner.
As one example, a bearing includes a bearing cap and bearing seat. The bearing cap includes two thrust control faces which extend perpendicular to the balancer shaft. On opposing sides of the bearing cap a first and second component are located. Thus, axial movement of the balancer shaft will cause one of the first or second components to contact one of the thrust control faces. This contact will limit the axial movement of the balancer shaft.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.